1. Field of the invention
The present invention relates to a device for sample feeding to combustion elemental analysis apparatuses. The device is of the type comprising a housing for the sample to be analyzed, said housing being provided in a movable support. The latter moves from a position where sample is received to a position of sample injection into the analytical instrument. In this position perfect sealing of the apparatus from external environment must also be ensured.
In the device, in correspondence with the movable support, the circulation of an inert gas is also foreseen for washing the sample housing.
2. Description of the Prior Art
Similar devices, already known in the art, receive a sample, generally contained in an envelope made of metal (e.g. tin), that must be submitted to qualitative and quantitative analysis of its components.
Obviously, the sample introduction into the analytical detection system must ensure that no other substances capable of altering the analysis are fed therewith, such as for example air present in the environment outside the apparatus.
For this purpose, combustion elemental analysis is performed in an atmosphere of inert gas, generally helium, that is used in the analytical apparatus both as sample washing gas and as carrier gas. This therefore involves a particularly accurate configuration in order to ensure perfect sealing, mainly in correspondence with the reciprocally moving parts, in order to avoid infiltrations of foreign elements that can affect analytical precision. Italian Patent IT 1122396, filed by Carlo Erba Strumentazione S.p.A., provides a sampler of the aforedescribed type, wherein a slide, sealingly movable within a seat, moves from a position where the sample coming from the external environment is received to a position where the sample is fed to the analytical apparatus, also ensuring in the latter position the insulation of the analytical environment from the external atmosphere.
The reciprocating movement of the slide is obtained by means of a double-acting cyclinder-piston pneumatic system. This solution is effective from the sealing point of view, but involves a considerable complication of the mechanisms driving the slide to achieve the necessary precision. Furthermore, possible increases in the number and size of the samples to be treated require to enlarge or replace the operating system thus jeopardizing the precision of movements and resulting in loss of reliability of the device.
A further drawback of the known devices is the fact that, with the slide use, particles of the analyzed samples fall on the slide and their accumulation leads to an increase in the sliding friction and therefore to an accelerated wear of the slide up to loss of sealing. Furthermore, maintenance operations become long and expensive due to the aforementioned complexity of the operating mechanisms of the device.
Said drawbacks are particularly important in the case of automatic feeders.